1. Field of the Invention
The invention relates to a security sheet such as a security paper and a method for manufacturing such a sheet.
2. Description of the Related Art
Security sheets such as security papers or films are used for manufacturing security documents such as banknotes, identity cards and the like. Conventionally, a wide variety of security features are incorporated into such security sheets or provided on their surface. Examples include watermarks, security threads and other banded security features. A problem with conventional security sheets is that it is often not possible to achieve high quality print on the sheet in view of the nature of the sheet material. It is also not possible to gain full potential from types of ink such as metallic/colour changing inks since these do not fully exhibit their optical characteristics due to absorption by the sheet material.
It is known in the case of certain papers to coat the paper so as to provide a better receptive surface for print but the problem with this approach is that the coating obscures the security features which have been incorporated in or onto the paper.
In accordance with one aspect of the present invention, a security sheet includes a viewable security feature on or in a substrate; and a print receptive coating on the substrate, the coating being registered relative to the security feature so that it does not overlap the security feature and so that the security feature is viewable from the same side of the substrate as the coating wherein the security feature is chosen from the group comprising watermarks, security threads and banded security features such as fibres or planchettes.
In accordance with a second aspect of the present invention, a method of manufacturing a security sheet comprises providing a substrate on or in which is provided a security feature; and providing a print receptive coating on the substrate in register with the security feature so that the coating does not overlap the security feature, and so that the security feature is viewable from the same side of the substrate as the coating wherein the security feature is chosen from the group comprising watermarks, security threads and banded security features such as fibres or planchettes, wherein the security feature is chosen from the group comprising watermarks, security threads and banded security features such as fibres or planchettes.
We have found that it is possible to partially coat the substrate with a print receptive coating so that the security feature is not obscured but much higher print quality can then be achieved by printing onto the coating. Additional security is also achieved since the presence of the coating will not immediately be obvious to the eye and by controlling the degree of registration, it will be possible to achieve high quality print features very close to the security features in a way which would be very difficult to counterfeit.